Method of forming indium tin oxide thin film using magnetron negative ion sputter source

Abstract

A method for forming an indium tin oxide thin film on a substrate in the present invention includes the steps of introducing a mixture of an inert gas and a low electron affinity element in close proximity to a target as a primary sputter ion beam source, providing an oxygen gas between the target and the substrate, applying an electrical energy to the target to ionize the mixture, confining electrons generated in the ionization in close proximity to a surface of the target facing towards the substrate, disintegrating negatively charged ions from the target, and forming the indium tin oxide thin film on the substrate.

What is claimed is:  
     
       1. A method of forming an indium tin oxide thin film on a substrate, the method comprising the steps of: 
       introducing a mixture of an inert gas and a low electron affinity element in close proximity to a target as a primary sputter ion beam source;  
       providing an oxygen gas between the target and the substrate;  
       applying an electrical energy to the target to ionize the mixture;  
       confining electrons generated in the ionization in close proximity to a surface of the target facing towards the substrate;  
       disintegrating negatively charged ions from the target; and  
       forming the indium tin oxide thin film on the substrate.  
     
     
       2. The method according to  claim 1 , wherein the negatively charged ions include In − , Sn − , O − , and O −   2 . 
     
     
       3. The method according to  claim 1 , further comprising the step of evacuating a process chamber prior to the step of introducing a mixture. 
     
     
       4. The method according to  claim 3 , wherein the low electron affinity element includes at least one of cesium, rubidium, and potassium. 
     
     
       5. The method according to  claim 1 , wherein the indium tin oxide thin film has at least 90% optical transmittance as well as a resistivity of an order of 10 −4  Ωcm. 
     
     
       6. The method according to  claim 1 , wherein the substrate is either grounded or positively biased with respect to the target. 
     
     
       7. The method according to  claim 1 , wherein the negatively charged ions have an ion beam energy approximately the same as a potential difference between the substrate and the target. 
     
     
       8. The method according to  claim 7 , wherein the ion beam energy decreases with an increase in a working pressure. 
     
     
       9. The method according to  claim 1 , wherein the substrate is maintained at a temperature in the range of about 25° C. to 100° C. 
     
     
       10. The method according to  claim 1 , wherein the substrate includes a glass. 
     
     
       11. The method according to  claim 1 , wherein the target has at least one through-hole therein, so that the mixture is diffused through the through-hole onto a surface of the target facing toward the substrate. 
     
     
       12. The method according to  claim 1 , wherein the electrical energy applied to the target is in the range of 25 to 1000 eV. 
     
     
       13. A method of forming an indium tin oxide thin film using a sputter system, the method comprising the steps of: 
       cleaning a substrate;  
       placing the substrate in a process chamber;  
       evacuating the process chamber where a sputter action occurs between a target and the substrate, wherein the target has first and second sides;  
       introducing a mixture of argon and cesium to the second surface of the target as a primary sputter ion beam source, wherein the target has at least one through-hole;  
       diffusing the mixture through the through-hole in the target from the second surface to the first surface;  
       providing an oxygen gas between the target and the substrate;  
       maintaining the process chamber to have a constant working pressure;  
       applying an electrical energy to the target to ionize the mixture;  
       confining electrons generated in the ionization in close proximity to the first surface of the target;  
       disintegrating negatively charged ions from the target; and  
       forming the indium tin oxide thin film on the substrate.  
     
     
       14. The method according to  claim 13 , wherein the negatively charged ions include In − , Sn − , O − , and O −   2 . 
     
     
       15. The method according to  claim 13 , wherein the substrate is either grounded or positively biased with respect to the target. 
     
     
       16. The method according to  claim 13 , wherein the substrate is maintained at a temperature in the range of about 25° C. to 100° C. 
     
     
       17. The method according to  claim 13 , wherein the substrate includes a glass. 
     
     
       18. The method according to  claim 13 , wherein the negatively charged ions have an ion beam energy approximately the same as a potential difference between the substrate and the target. 
     
     
       19. The method according to  claim 18 , wherein the ion beam energy decreases with an increase in the working pressure. 
     
     
       20. The method according to  claim 13 , wherein the electrical energy applied to the target is in the range of 25 to 1000 eV. 
     
     
       21. The method according to  claim 13 , wherein the indium tin oxide thin film has at least 90% optical transmittance as well as a resistivity of an order of 10 −4  Ωcm.